[Networking] Assume that there are u users connected to the University of Delhi\

Question

[Networking] Assume that there are u users connected to the University of Delhi's wireless network to connect to the Internet. u = 1000 during the day, and r = 600 during the night. These users want to brows some Web sites, and the average number of HTTP requests generated by all the users is 0.5 × u requests per second. Assume that the size of 1 HTTP request messages is negligible, but each HTTP response message returns an object of size 500 Kbits. If the university is connected to the Internet through a 700 Mbps access link,

(a) What is the percentage of access link’s capacity consumed by the HTTP response messages during the day and night?

(b) What is the percentage of access link’s capacity consumed by the HTTP response messages during the day if we use a Web cache which can directly respond to HTTP requests with probability h?

Explanation / Answer

provided u=1000 and r=600

for day time

HTTP requests generated per second =0.5 * 1000=500 requests/sec

Respone size per second= 500Kbits

for night time

HTTP requests generated per second =0.5 * 600=300 requests/sec

Respone size per second= 500Kbits

a) for day time:

per second accessed data = (no of request)*(response size)=500*500=250000kb=250000/1024 mb=244.14mb

that is access link’s capacity consumed by the HTTP response messages during the day=(244.14/700)*100 %=34.88%

for night time:

per second accessed data = (no of request)*(response size)=300*500kb=150000/1024 mb=146.48 mb

that is access link’s capacity consumed by the HTTP response messages during the day=(146.48 /700)*100 %=20.92%

b)

the probablity of finding the request in the cache is h.

so probablity of not finding the request in the cache is (1-h).

so in this scenerio the the answer will be =(1-h)*34.88%.

because we need consider only the non hit cases of the requests in the cache.

)*500*500

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